Igniter device



Of- 6, 1964 L. .1. BQRNSIELN 3,115211,447'1 :EGNITERI DEVICE;

Filed Aug. l2. lQGO 2 Sheets-Sheet l NIL mm -l1 mm O co0 o Oo l ATTORNEYOct. 6, 1964 L. J. BoRNsrElN 3,151,447

IGNITER DEVICE 2 Sheets-Sheet 2 Filed Aug. l2, 1960 INVENTOR. LAWRENCEJ. BORNSTEIN f@ ATTORNEY United States Patent O 3,151,447 IGNITER DEVICELawrence d. Bernstein, Sacramento, Calif., assigner t Aei'ojet-GeneralCorporation, Azusa, Calif., a corporation of thio Filed Aug. 12, 1960,Ser. No. 49,383 6 Claims. (Cl. 60-35.6)

This invention relates to rocket motors and more particularly to meansfor igniting the propellant within the rocket motor.

In accordance with the present invention, the principal object is toprovide a rocket motor igniter that may be armed after the completeassembly of the rocket motor and missile.

Jet propelled devices such as rocket motors ordinarily comprise acombustion chamber, a charge of fuel within the chamber, and an exhaustnozzle through which the gases, resulting from combustion of the fuelcharge, pass at high velocity to create propulsive thrust. It is commonto install an igniter within the charge during the assembly of therocket motor. However, it is entirely possible to detonate the igniteraccidentally.

According to my invention, it is possible to fully assemble a rocketmotor with a warhead and electronic guidance instrumentation into anintegral missile unit without any possibility of accidental ignition ofthe rocket motor. The invention is carried out by installing a containerof pyrotechnic material within the rocket motor during assembly. Thelast step prior to launching is to install an electric squib which isconnected to the combustion chamber exterior and communicates withchamber interior, being accessible from the rocket motor exterior.

Briefly, the present invention comprises the combination of a porousigniter basket containing a pyrotechnic material fastened to the rocketmotor housing and extending into the interior of the solid propellant,and an electric squib is inclined at an angle to the igniter andattached to the rocket motor housing. An access port through the rocketmotor allows the insertion or removal of the electric squib from theassembled rocket motor and missile.

The foregoing and other features of my invention will be betterunderstood from the following detailed description taken in conjunctionwith the accompanying drawings of which:

FIGURE 1 is a partial longitudinal cross section showing the igniter andsquib according to the present invention,

FIGURE 2 is an end view of the present invention shown with the warheadremoved,

FGURE 3 is a cross section of the igniter taken along line 3 3 in FGURE1,

FIGURE 4 is a cross sectional View of another embodiment of the igniterof the present invention; and

FIGURE 5 is a cross section of the igniter taken along line 5 5 inFIGURE 4.

Referring to FIGURES 1 and 2, the rocket motor 10 is substantiallycylindrical in configuration and includes a housing 13 with a solid fuelgrain propellant 11 mounted inside in a manner well known in the art.The housing has a bell-shaped end cap 12 xedly attached to one of theopen ends. niter element 14. An adapter 16 is attached to the end cap asfor example, by welding, and provides an attaching device for theigniter element 14. The igniter element comprises a plug 18 that isthreadedly received by the adapter lo and is in sealing engagementtherewith by interposing the gasket 20 between the adapter 16 and theplug threads. The configuration of the plug 18 may be as shown with ahexagonally-shaped head to facilitate Centrally located in the end capis an ig-` ice the end cap 12. Numerous configurations of the plug 18lmay be used to accommodate assembly by any means.

A snout 22 extends from the head of the plug 18 suiiiciently within therocket motor interior to allow the perforate igniter basket 24 to besupported thereby. I A cavity 26 in .the plug snout 22 receives a heatinsulator 28 such as Zinc stearate or the like. The igniter 14 nestswithin the cavity 15 of the solid propellant 11.

The igniter basket 24 extends longitudinally Within the correspondinglyshaped recess 25 in fuel grain 11 of the rocket motor interior. Theembodiment illustrated in FIGURE 1 is an example of the possible shapeof the igniter basket. The igniter basket 24 is formed as an elongatedcylindrical member having its side wall and end wall formed integrally.A plurality of orifices 3G extends through the side and end walls of thebasket and are used to allow hot gases to be distributed uniform- Y 1yin all directions from the igniter when in operation. Glass fibers orrovings impregnated by a suitable plastic material such as epoxy orpolyester resins are suitable materials to fabricate the basket 24.Other suitable materials such as perforated metal or wire mesh can beused to form the basket 24. The only requirement of the basket 24 is toretain the combustible charge until completely consumed and should notbecome broken or disintegrated in operation. A suitable plastic glassfiber igniter basket is the subject -of a patent application bearingSerial No. 708,583, tiled l'anuary 13, 1958 by Herman Schneiderman etal., now Patent No. 3,021,241 and assigned to the same assignee as thesubject patent application.

The partitions 32, 34 are cylindrically shaped and have a plurality ofpassageways 36, 38 therethrough. The basket 24 has the partitions 32, 34placed at its open and closed ends to confine the pyrotechnic material40 con tained therein.

A plastic tape (not shown) may be wrapped around the basket 24 toprevent the pyrotechnic material 40 from falling out of the orifices. Awaterproof covering (not shown) may shield the plastic tape from weatherdeteriora-` tion.

The igniter basket 24 may be iilled with any suitable pyrotechnicmaterial 40. For example, a suitable mixture is 13 parts by weight ofblack powder and 100 parts by weight of a pyrotechnic compositiondisclosed in the copending patent application bearing Serial No.309,039, led September ll, 1952, by Calvin A. Gongwer now t Patent No.3,019,687 and assigned to the same assignee as installation and removalof the igniter element I4 within f the present invention.

The tube 50 is fixedly attached to the end cap 12 and may be positionedradially, as shown in FIGURE 2, and at an oblique angle to thelongitudinal axis C of the rocket motor 1li as shown in FIGURE 1. Anelectric squib or hot gas generator or initiator 52 is received by thetube 50 and extends within the rocket motor 1t) inside recess 51 in fuelgrain 11 and is directed toward the igniter 14. For reasons to becomeapparent below, recesses 25 and 51 communicate with each other. Theangle between the electric squib 52 and the igniter 14 is variable,depending upon the distance between these two components, the size ofthe basket orifices, and the type of ignitible material being used. Inthe present embodiment a 60 angle exists between electric squib 52 andthe igniter 14.

The electric squb or initiator S2 has a plug 54 that is threadedlyreceived by the tube Si). A shell 56 is threaded at one end into theplug 54 Yand has an elongated neckeddown snout 58 that extends from theplug 54 through the tube and into the rocket motor. The 0 ring seal 53is positioned between the plug 54 and the tube 50 to prevent gas leaksfrom the interior of the rocket motor 10. A passageway 60 extendsthroughout the shell 55. The squib 52 consists of a paper, metallic, orplastic encased pyro- E technic material 64 having a high resistanceelectrical wire 66 contained therein for ignition purposes. A cavity 113is provided in the propellant grain 11 to admit the electric squib intothe rocket motor interior.

Although the squib 52 is shown in FiGURE l at an angle to the igniterelement 14, it is within the present invention to place the squib 52 inany angle or in juxtaposition relative to the igniter element 14.

The paper, metallic, or plastic encased pyrotechnic material 64 iscemented to the interior of the shell 56 as for instance, by an epoxyresin adhesive, and is partially positioned at one end by a recess 62.The opposite end of the paper, metallic, or plastic encased pyrotechnicmaterial 64 is directed toward the open end of the shell 56. The wires66 extend upwardly toward the plug S4 and are attached to the leads 63.A potting material 70 supports the leads 68 and wires 66 to keep themfrom shorting out against the plug 54. A port i3 in the rocket motoraffords access to the squib 52 after the entire rocket is assembled intoa missile or a completed unit.

To operate the igniter element i4 and initiator or squib 52 assembly,the leads 68 are connected to a suitable electric source (not shown)positioned exteriorly of the rocket 110. Application of an electricalcurrent to the wires 66 instantaneously ignites the pyrotechnic material64 within the squib 52 and the resulting flames shoot outwardly throughthe passageway 60 of the shell 56. The issued iiames impinge upon theigniter 1.4 entering the orifices in the basket 24 and ignite thepyrotechnic material 40 contained therein. Complete ignition of thepyrotechnic material 40 causes sparks (point sources of heat) to beprojected from the basket orifices 30 thereby igniting the rocket motorpropellant grain in the immediate proximity of the igniter.

Referring to FIGURES 4 and 5, another embodiment of the igniter isshown. Substantially the same basket 24 and plug 18 are used as shown inthe igniter 14 in FIG- URE 1. An inner screen 70 of an elongatedcylindrical configuration extends concentrically to the axis B of theigniter 71. This inner screen '70 provides a cavity or channel throughwhich the entire length of the pyrotechnic material may be ignited.Surrounding the screen 70 is a second screen 72 of a similar congurationbut of a larger diameter. The second screen 72 is supported in positionat the plug end of the igniter 71 by a pair of annulus-shaped separators74, 76. A first pyrotechnic material 78 such as a black powder or thelike, nests between the screens 70, 72 and at the area between theseparators 74, '76, extends to abut the interior of the i.,- niterbasket 24. A second pyrotechnic material 80 having a slower burning ratethan the tirst pyrotechnic material 7S is packed between the secondscreen 72 and the igniter basket 24. The second pyrotechnic material maybe, for example, a mixture of 13 parts by weight of black powder and 100parts by weight of the solid propellant described in the patentapplication bearing the Serial No. 708,583, filed January 13, 1958, byHerman Schneiderman, et al., now Patent No. 3,021,241, and assigned tothe same assignee as the present invention.

The operation of the embodiment, shown in FIGURES 4 and 5, is quitesimilar to the operation of the assembly shown in FIGURE 1. The squib 52is positioned with the passageway 60 of the shell 56 directed at thearea between the partitions '74, 76 of the igniter basket 24. The fiamesissued from the squib 52 easily ignite the first pyrotechnic material 78contained therein. The first pyrotechnic material 78 burns along itsentire length adjacent to the screen 70. Thereafter, subsequent ignitionof the second pyrotechnic material 80 causes hot gases to issue throughthe orifices 30 and impinge upon the solid propellant contained Withinthe rocket motor.

It should be understood that the description and drawings employed inthe above specification are given by way of example rather than oflimitation; and the invention is not limited except by the scope of theappended claims.

I claim:

1. An igniter element comprising: a hollow elongated basket closed atone end and having a plurality of orifices therethrough, a cap memberfixedly attached and closing tbe open end of said basket, a first hollowelongated container concentrically positioned within the basket, asecond hollow elongated container received by said basket andsurrounding said rst container, a rst rapidly burning easily ignitedpyrotechnic material received between said rst container and said secondcontainer, and a second slow burning pyrotechnic material receivedbetween said basket and said second container.

2. An igniter element as defined in claim 1 in which the tirstpyrotechnic material extends through said second pyrotechnic material toat least one of said orifices in said basket.

3. An igniter element as deiined in claim 1 in which the firstpyrotechnic material extends through said second pyrotechnic material toat least one of said orifices in said basket, and means for insulatingthat portion of said first pyrotechnic material extending through saidsecond pyrotechnic material from said second pyrotechnic material.

4. An apparatus of the class described comprising a rocket motor, saidrocket motor mounted in a housing, said rocket motor housing having afirst opening formed therein, a perforate basket removably mounted inthe first opening, a pyrotechnic material in said basket, a secondopening in said rocket motor housing, communieating with the perforateWalls of said basket, a hot gas generating means removably mounted insaid second opening of said rocket motor housing and directed againstthe perforate walls of said basket, whereby when the hot gas generatingmeans is actuated, the hot gas penetrates the walls of the basket andignites the pyrotechnic material in the perforate basket to stant therocket motor.

5. in an apparatus as defined in claim 4, said pyrotechnic materialbeing formed in a plurality of distinct concentric layers, the inner oneof said layers being cornposed of rapid burning, easily ignitablepyrotechnic material and the outer one of said layers being composed ofslow burning pyrotechnic material.

6. In a rocket motor, a solid fuel grain, said solid fuel grain having afirst recess formed therein, a perforate basket removably mounted insaid first recess in said solid fuel grain, a pyrotechnic material insaid perforate basket, a removable closure for said basket to seal thebasket and pyrotechnic material in the fuel grain, said solid fuel grainhaving a second recess communicating with said first recess, a hot gasgenerating means removably mounted in said second recess in said solidfuel grain, said hot gas generating means in said second recess of saidsolid fuel grain directed so when it is actuated, the hot gas impingeson and penetrates the perforate walls of the basket to ignite thepyrotechnic material in the perforate basket causing it to ignite thesolid fuel grain and start the motor.

References Cited in the file of this patent UNITED STATES PATENTS1,530,692 Paulus Mar. 24, 1925 2,434,652 Hickman Jan. 20, 1948 2,516,898Meister Aug. l, 1950 2,743,580 Loeb May 1, 1956 2,934,014 Smith et al.Apr. 26, 1960 2,973,713 Burton Mar. 7, 1961 3,011,441 Gordon Dec. 5,1961 3,014,425 Turnvull et al Dec. 26, 1961 FOREIGN PATENTS 958,434France Sept. l2, 1949 15,111 Great Britain Nov. 20, 1886 26,909 GreatBritain Dec. 5, 1907

4. AN APPARATUS OF THE CLASS DESCRIBED COMPRISING A ROCKET MOTOR, SAIDROCKET MOTOR MOUNTED IN A HOUSING, SAID ROCKET MOTOR HOUSING HAVING AFIRST OPENING FORMED THEREIN, A PERFORATE BASKET REMOVABLY MOUNTED INTHE FIRST OPENING, A PYROTECHNIC MATERIAL IN SAID BASKET, A SECONDOPENING IN SAID ROCKET MOTOR HOUSING, COMMUNICATING WITH THE PERFORATEWALLS OF SAID BASKET, A HOT GAS GENERATING MEANS REMOVABLY MOUNTED INSAID SECOND